This invention is generally directed to metal phthalocyanines and processes for the preparation thereof, and more specifically the present invention is directed to processes for obtaining halo, preferably chloroindium phthalocyanine, and layered photoconductive members comprised of the aforementioned phthalocyanine. In one embodiment, the present invention is directed to a process for the preparation of chloroindium phthalocyanines by initially heating a mixture of indium trichloride and a phthalodinitrile, such as ortho-phthalodinitrile in a mixture of solvents comprised of a dialkylaminoalkanol and a second high boiling solvent such as a chlorinated hydrocarbon; cooling the mixture to enable precipitation; and optionally separating the desired chloroindium phthalocyanine from the solution followed by an optional washing. The chloroindium phthalocyanine prepared by the processes of the present invention, can be selected as photogenerator materials or pigments in photoresponsive imaging members. The aforementioned photoresponsive imaging members may contain separate charge, especially hole transport layers such as arylamine hole transport molecules. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate, or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductor imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and other printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of the appropriate charge. Generally, the imaging members are sensitive in the wavelength regions of from about 700 to about 850 nanometers, thus diode lasers can be selected as the light source. Chloroindium phthalocyanines may also be selected as intense blue light-stable colorants for use in coatings, such as paint, inks, and as near infrared absorbing pigments suitable for use as IR laser optical recording materials.
Certain chloroindium phthalocyanine pigments are known, see for example, the .alpha. and .beta. polymorphs, reference, for example, "Uber die Polymorphie der Indium phthalocyanine" by P. Muhl, in Kristall and Technik, Vol. 2 page 431 to 435, Akademie-Verlag, 1967, D. Colaitis, in Bull. Soc. Chim., page 23, 1962, and R. O. Loutfy et al., in Journal of Imaging Science, Vol. 29, No. 4, July/August, 1985, pp. 148 to 153. However, unlike some other phthalocyanines such as metal-free, copper, iron, and titanyl phthalocyanines, chloroindium phthalocyanines have had minimum general commercial use as pigments, or in electrophotographic or optical recording applications. In U.S. Pat. No. 4,555,463, there is illustrated a layered imaging member with a chloroindium phthalocyanine photogenerating layer, which chloroindium phthalocyanine may be prepared as described in Inorganic Chemistry, 1980, Vol. 19, pages 3131 to 3135, the disclosures of these references being totally incorporated by reference herein in their entirety. The use of photoreceptor devices incorporating chloroindium phthalocyanine is described in the aforementioned publication Journal of Imaging Science, Vol. 29, No. 4, July/August, 1985, pp. 148 to 153. Additionally, the utilization of chloroindium phthalocyanines or titanyl phthalocyanine in a multilayered electrographic device is illustrated in Japanese Patent Application Laid Open (Kokai) No. 59-166959. Other patents of interest which use chloroindium phthalocyanine and or derivatives for the preparation of photoconductive devices thereof include U.S. Pat. Nos. 4,587,189 and 4,471,039.
Several procedures for preparing haloindium phthalocyanines, such as chloroindium phthalocyanines are known. Some of the preparative methods result in phthalocyanines with halogen substituents on both the indium atom and the phthalocyanine ring. Such synthetic routes usually involve the reaction of o-phthalodinitrile with indium chloride in the absence of any solvents, such as described by G. P. Shaposhnikov, et al., in Izv. Vyssh. Uchebn. Zaved., Khim. Techol., 20, pages 184 to 186, 1977. The same synthesis was used in Example I of U.S. Pat. No. 4,47 1,039 and Example I of U.S. Pat. No. 4,587,189. In both process situations, the reaction product was chloroindium chlorophthalocyanine, with partial ring chlorination (about 0.67 to 0.75 molecule of chlorine per phthalocyanine ring).
Synthetic methods which yield haloindium phthalocyanines with no ring halogenation for practical purposes, that is, within the limits of analytical methods for halogen, usually involve the use of a high boiling reaction solvent, such as quinoline, chloronaphthalenes, and the like. A typical synthesis is described by J. P. Linsky et al., in Inorg. Chem., 19, 1980, page 3131 to 3135 and involves the reaction of o-phthalodinitrile with indium chloride in doubly distilled quinoline under reflux with a product yield of about 50%. A second typical synthesis involves the reaction of 1,3-diiminoisoindoline with indium chloride in quinoline, under reflux (at about 238.degree. C.) for 6 hours with a yield of about 50%. This procedure also requires the synthesis of the precursor 1,3-diiminoisoindoline from o-phthalodinitrile, which increases the complexity and the cost of the process if a commercial implementation is contemplated.
U.S. Pat. No. 4,731,312 issued Mar. 5, 1988, to Kato discloses the preparation of electrophotographic members comprising certain indium phthalocyanines, XInPc where X is a halogen, as photoconductive materials in the charge carrier or generation layer. The reaction of o-phthalodinitrile and indium chloride in refluxing quinoline results in the formation of the desired chloride indium phthalocyanine. The product, however, is believed to be accompanied by other unidentified products or impurities considering the large variance observed in the reported empirical formula or ratio of elements. No yield or isolation details are provided. The chloroindium phthalocyanine used in the Japanese Patent Application Laid Open (Kokai) No. 59-166959, was synthesized by reacting o-phthalodinitrile and indium chloride in alpha-chloronaphthalene solvent at 250.degree. C.
In the aforementioned documents, synthesis and processing conditions were disclosed for the preparation of the chloroindium phthalocyanine pigments which lead to relatively low reaction yields of up to about 50%, and to pigments which need additional extensive purifications before the pigments could be effectively used in certain electrophotographic applications.
To obtain a chloroindium phthalocyanine (CIlnPc) based photoreceptor having high sensitivity to near infrared light, it is believed necessary to control the purity and chemical structure of the pigment as well as to prepare the pigment in the correct crystal modification.
In view of a variety of potential applications of chloroindium phthalocyanine pigments there is a need for economically viable processes in which the pigments are obtained in high purity and acceptable yields. Synthesis yields of a minimum of 75% are generally targeted for large scale, economical processes in which readily available raw materials and solvents are selected. Disadvantages of the prior art processes for preparing chloroindium phthalocyanine compounds include: having to employ a stoichiometric excess of the indium chlorides; the product is frequently contaminated with undesirable by products, for example, metal free phthalocyanine; use of commercially difficult to source materials such as 1,3-diiminoisoindoline or high purity quinoline; and particularly the yields are typically about 50% or less and economically unattractive for larger scale (multi-kilo) production operations.
In the present application, there is disclosed, for example, in one embodiment a high yield, high purity, and economical process for the preparation of chloroindium phthalocyanine. This method is an improvement over the prior art in that, for example, in embodiments thereof, the process is not complex, is rapid, and uses commercially readily available raw materials and solvents. Both the yield and the quality of the pigments often depends on synthesis conditions, for example, the solvent selected for use in the reaction. The high yield of the present process, compared to the processes described in the prior art, is achieved in embodiments by a synergistic effect, that is, by the use of a mixture of at least two solvents which includes an alkylalkanolamine such as a dialkylaminoethanol. The process of the present invention in one embodiment involves heating a mixture of indium trichloride and ortho-phthalodinitrile in a mixture of solvents comprised of a dialkylaminoalkanol and a high boiling second solvent resulting in a yield that is greater than what one would obtain with either solvent separately or individually.
U.S. Pat. No. 3,657,272 issued Apr. 18, 1972, discloses a direct process for preparing metal-free phthalocyanine comprising the steps of mixing o-phthalodinitrile in an ammonia-saturated alkylalkanolamine solvent, seeding the mixture with a catalytic amount of X-form phthalocyanine, heating said mixture to reflux temperature and maintaining said temperature for about 20 to about 70 minutes, and filtering the hot reaction product formed thereby. The metal-free phthalocyanine process described U.S. Pat. No. 3,657,272 is unique because it affords a direct synthesis of metal-free phthalocyanine instead of the previous art which involved intermediate synthesis of sodium phthalocyanine or other metal phthalocyanines, followed by demetallization to metal-free phthalocyanine. Metal-free phthalocyanine could not be synthesized directly by methods used for metal phthalocyanines synthesis in meaningful yields. It is believed that the alkylalkanolamine as used in the '272 reference is an active solvent in the reaction, that is, the solvent is believed to be participating in the intermediate reaction steps which lead to the formation of the metal-free phthalocyanine product.
The disclosures of all the aforementioned publications, and patents are totally incorporated herein by reference.